HCPL-316J-500E Datasheet, PDF (31/33 Pages) AVAGO TECHNOLOGIES LIMITED – 2.5 Amp Gate Drive Optocoupler with Integrated (VCE) Desaturation Detection and Fault Status Feedback

Thermal Model
The HCPL-316J is designed to dissipate the majority of
the heat through pins 4 for the input IC and pins 9 and 10
for the output IC. (There are two V_EE pins on the output
side, pins 9 and 10, for this purpose.) Heat flow through
other pins or through the package directly into ambient
are considered negligible and not modeled here.
In order to achieve the power dissipation specified in
the absolute maximum specification, it is imperative
that pins 4, 9, and 10 have ground planes connected to
them. As long as the maximum power specification is
not exceeded, the only other limitation to the amount
of power one can dissipate is the absolute maximum
junction temperature specification of 125°C. The junc-
tion temperatures can be calculated with the following
equations:
T_ji = P_i (T_i4 + T_4A) + T_A
T_jo = P_o (T_o9,10 + T_9,10A) + T_A
where P_i = power into input IC and P_o = power into out-
put IC. Since T_4A and T_9,10A are dependent on PCB layout
and airflow, their exact number may not be available.
Therefore, a more accurate method of calculating the
junction temperature is with the following equations:
T_ji = P_iT_i4 + T_P4
T_jo = P_oT_o9,10 + T_P9,10
These equations, however, require that the pin 4 and pins
9, 10 temperatures be measured with a thermal couple
on the pin at the HCPL-316J package edge.
From the earlier power dissipation calculation example:
P_i = 90.8 mW, P_o = 217.3 mW, T_A = 100°C, and assuming
the thermal model shown in Figure 77 below.
T_ji = (90.8 mW)(60°C/W + 50°C/W) + 100°C
= 110°C
T_jo = (217.3 mW)(30°C/W + 50°C/W) + 100°C
= 117°C
both of which are within the absolute maximum specifi-
cation of 125°C.
If we, however, assume a worst case PCB layout and no
air flow where the estimated q_4A and q_9,10A are 100°C/W.
Then the junction temperatures become
T_ji = (90.8 mW)(60°C/W + 100°C/W) + 100°C
= 115°C
T_jo = (217.3 mW)(30°C/W + 100°C/W) + 100°C
= 128°C
The output IC junction temperature exceeds the abso-
lute maximum specification of 125°C. In this case, PCB
layout and airflow will need to be designed so that the
junction temperature of the output IC does not exceed
125°C.
If the calculated junction temperatures for the thermal
model in Figure 78 is higher than 125°C, the pin temper-
ature for pins 9 and 10 should be measured (at the pack-
age edge) under worst case operating environment for a
more accurate estimate of the junction temperatures.
T_ji
θ_i4 = 60°C/W
T_P4
θ_4A = 50°C/W*
T_jo
θ_O9,10 = 30°C/W
T_P9,10
θ_9,10A = 50°C/W*
T_A
T_ji = junction temperature of input side IC
T_jo = junction temperature of output side IC
T_P4 = pin 4 temperature at package edge
T_P9,10 = pin 9 and 10 temperature at package edge
T_I4 = input side IC to pin 4 thermal resistance
T_I9,10 = output side IC to pin 9 and 10 thermal resistance
T_4A = pin 4 to ambient thermal resistance
T_9,10A = pin 9 and 10 to ambient thermal resistance
*The T_4A and T_9,10A values shown here are for PCB layouts shown
in Figure 78 with reasonable air flow. This value may increase or
decrease by a factor of 2 depending on PCB layout and/or airflow.
Figure 78. HCPL-316J thermal model.
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